Topic: Should we allow filter-turning through cycleway movements?

At the 2018 SNUG workshop, Megan gave a presentation on the possibility of allowing vehicles to filter-turn through cycle movements coming from protected cycleways, and Axel led a discussion afterwards.  We’d like to continue this discussion on the SNUG forum – the following are some discussion points that were raised, and ViaStrada’s current stance, you’re invited to suggest an alternative position, and also raise other related points that you feel should be considered.

  1. The group seems generally supportive of trialing filter-turning across cycle movements from separated cycleways provided the location is suitable, and the treatment includes partial protection plus some indication to drivers to remind them to first give way to cyclists. 

  2. Someone raised the concern that flashing yellow already means “caution”. 

    • ViaStrada suggests that “caution” is a good attitude to apply to filter-turning, as it reminds drivers to look for and give way to cyclists.

                    *    The road code teaches “A flashing yellow signal means the traffic signals are not working. In this case, you must apply the give way rules for uncontrolled intersections.” 
                    *    The flashing yellow arrow would be the only flashing yellow aspect at the intersection, therefore distinguishing the situation from that where all signals were in flashing yellow mode and give way rules apply to everyone.
                    *    The flashing yellow arrows would be applied to turns across a cycleway – the only movements they’d have to give way to would be cyclists and pedestrians (and potentially opposing traffic, if the flashing yellow arrow were applied against a right turn).
                    *    The device would need to be accompanied by promotion / education.

  3. Someone suggested using a flashing green arrow instead of a flashing yellow arrow.

    • ViaStrada is worried that drivers will think “green means go” and assume they have a protected turn, even if the signal is flashing.

                    *    This pre-conception is riskier than the pre-conception that flashing yellow means caution and would likely be more difficult to address with promotion / education.
                    *    No other country is known to use flashing green arrows to indicate filter turning.  NCHRP Research Report 493 details how five signal displays for “protected / permissive” (i.e. full / filter) turn control were evaluated; flashing green arrows were not considered, and flashing yellow arrows were identified as preferred.  In eastern Canada, flashing green discs can be used to indicate a protected turn, but these are being replaced with steady green arrows.

  4. Where would a flashing yellow arrow be integrated in a traditional display?

    • In the USA, it is necessary to provide the flashing yellow arrow as a separate aspect to the steady yellow arrow – ViaStrada suggests NZ should adopt this principle, as it would help distinguish the flashing yellow arrow. 

    • Therefore, the flashing yellow arrow would be located below the regular yellow arrow.  In most locations, it is unlikely that the turn would be operated sometimes as a filter and sometimes as fully protected, so it is unlikely that a green arrow would be required.  If there is need for a green arrow, it could be incorporated in the same aspect as the flashing yellow arrow (using LEDs), or as a separate aspect below the flashing yellow arrow aspect (less ideal, as this would result in a non-standard 4-aspect signal column).

  5. An alternative to using flashing arrows was suggested: yellow road studs indicating cyclists approaching.

    • ViaStrada considers this would be a good complementary treatment, but it may not be directly associated with filter turning.

                    *    Significant education, and possibly supplementary signage, would be required.

  6. Another alternative suggested was having a flashing yellow bike symbol (similar to the cyclist-activated warning signs used on narrow bridges).

    • In Germany, a flashing beacon with pedestrian and / or cycle symbol (“schutzblinker”) can be applied at intersections where turning traffic filters across a pedestrian crosswalk or cycle movement.  Flashing yellow beacons are used in Denver at non-signalised intersections along a pilot cycleway corridor. 

    • ViaStrada suggests that such a device may be a better alternative to flashing yellow arrows than yellow road studs, as it would include a cycle symbol and therefore make the point of the flashing clearer to motorists.

Re: Should we allow filter-turning through cycleway movements?

Flashing yellow arrows seem to me to be the best way to enable turning vehicles to safely filter through cycle and pedestrian movements.  I've seen them used in Perth and Sydney very successfully for pedestrian protection.

I don't agree with having the flashing yellow as a separate aspect to the solid yellow.  Motorists should easily be able to distinguish between a 0.5sec flash of yellow and 4.0sec of steady yellow and you would expect that the speeds of the turning movements would be low, so even missing the first 1-2sec of steady yellow (thinking it is still flashing) would mean there is still 2-3sec of warning that the movement is terminating.

In Chch, we currently have a left turn movement crossing a separated cycle movement which has a 3-aspect arrowed display since it is part of a double diamond overlay operation, so the green arrow exists.

Also, if we get a yellow arrow included as a legal display, then I can't see why we wouldn't use it to provide right turn protection for pedestrians at sites that have right turn green arrows, so combining the steady yellow and flashing yellow would be imperative.  It would also mean that there are no hardware changes required at these sites and the flashing yellow could be implemented with a software change only.